Drying kiln



NW. 245 wm. H F ,www 1,833,397.

DRYING KILN Filed OCT.. l. 1928 2 Sheets-Sheet l Ewenor Nov. 24, 1931 H.F. HAGEN j DRYING KILN Filed Oct.

l. 1928 2 Sheets-Sheet 2 O o o o o o .o o

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o o o o o o o o o Paten-ted Nov. 24, 1,931

4UNITI-1D STATES PATENT o FFICE HAROLD F. HAGEN, OF DEDHAM,MASSACHSETTS, ASSIGNOR T0 B. F. STURTEVAN T COM- PANY, OF HYDE SPARK,MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS p DRYING KILN Applicationmea oe'tob.er 1,1e2a serial Naeoaeos.A

The kilns.

In the drying of many materials such, for example, as lumber, it is verydesirable that present invention relates to drying the drying shallproceed throughout the,

mass of material at the same rate, thus making it possible to obtainthedesired degree of dryness, whatever ,it may be, for the entireproduct. In order to accomplish this result it is necessar that thedrying air shall flow over and through the entire mass of material insubstantially uniform amount and velocity, and it is the object of thepresent invention to provide a construction of Ydrying kiln whereby suchflow will be secured.

With this object in View the present invention consists of a drying kilnin which means are provided for securing a u niform and evendistribution of the drying air throughout the transverse areas of thedrying room or chamber, and for maintaining a constant head or pressuredifference between oppoesd points of such transverse areas. Theseresults are obtained according to the present invention by providing thewalls at opposite sides of the drylng room or chamber, transverse to thepath of air flow, with` uniformly distributed or spaced orilices for thepassage of air therethrough,and supplying the drying air at a constantpressure to the inlet wall orifices. The loss of head measured from anypoint on the inlet or supply wall to a point on the outlet or returnwall directly opposite thereto will, therefore, be the same as the lossof head between any y other similarly opposed points on the surfaces ofthe walls,vand the flow of air across the drying room or chamber will bethe same in amount and velocit throughout the entire transverse sectionof t .e room.

An important feature of the present invention consists in supplying theair through the ducts at a relatively high pressure, and admitting it tothe dryingchamber at a relatively low velocity. This is accomplishedthrough the provision of a wall onthesupply side ofthe drying chamberconsisting of two parallel partitions closely spaced and provided withuniformly arranged'orifices.

l plied to a kiln for drying lumber,

The space between the partitions forms a pressure chamber in which auniform pres. sure head is maintained, with low velocity of flow. Byproviding the outer partition which lies between the air supply duct andsuch ressure chamber with orifices of considera ly less totalcrossfsectional area than those in the inner Wall between the pressurechamber and the dryingchamber, and having the orifices in the twopartitions out of register, a very uniform pressure of reduced amountwill be vmaintained throughout this pressure chamber in the inlet wall,and a correspondingly highly uniform ow ,of air at reduced velocitysecured throughout the entire inner partition and into the dryingchamber. By the provision of an outlet or return wall provided withuniformly spaced orifices leadin to the return ducts, the evendistribution o drying air across the entireV width of the chamber ismaintained. In the accompanying drawings illustrating the preferred formof the invention vas ap- Fig. 1 is a horizontal sectional view of asmuch of the kiln as isv necesasry to describe the present invention;Fig. 2 is a sectional end elevation of the kiln; Fig. 3 is a verticalside elevation through the drying room of the kiln; Fi ..4 is a sideelevation of a section of the dou le plate wall on the drying room side;Fig. 5 is an elevation of a plate forming part of the return wall; andFig. 6 is a section on line 6-6 of Fig. 4.

The illustrated kiln comprises a cement foundation 8 and insulated outerWalls 10 `and a roof 12. The kiln is divided into a fan l `stacked ontrucks 24 and rolled into the drying rooms on suitable rails in theusual manner. As 4shown in Fig. 3, the material to be dried comprisesplanks 26 of wood arranged in horizontal rows and separated by the usualshown in Figs. 1 and 3, there are being three inches transverselyarranged stickers 28. Itis desirable that the material be stacked 'asuniformly `as possible in order to present uniform resistances to thecurrents of air passing through the dryin rooms.

The partitions etween the separate drying rooms constitute a part of thesupply and return ducts through which the air passes between the fan andthe drying rooms. As two supply ducts 30, between the first and Asecondand between the third and fourth drying rooms, a return duct `32 in themiddle of the kiln between the second and third drying rooms, and returnducts 34 at the sides of the kiln. Conduits 36 connect the outlet of thefan with the supply ducts 30, andthe return ducts 32 and 34 return theair to the conditioning apparatus 2O through suitable conduits 38.

Considering the`right hand drying room of Fig. 3 which is shown in theupper part of Fig. 1, this drying room has a wall or partition 40 on'thesupply si e and a wall or artition 42 on the return side, these wallseing parallel to each other and perpendicular to the-paths of air flowthrough the drying room. Each wall is made up as shown 1n Fig. 2 of aplurality of sections, each provided with orifices to permit the air topass therethrough. As shown in Figs. 4 and 6, the inlet or supply wall40 is composed of a pluralit 'of sections indicated generally at 44whic'llv are secured to suitable. studs 46 and horizontal stringers 48.Each section 44 comprises two opposed closely spaced plates 50 and 52.The plate 50 which is on the supply or duct side of the wall has anumber of orificesi54 and the plate 52 on the drying room side has arelatively greater number of orifices 56. These openingsin the twoplates, as shown. in Fig. 4, are not in register. The side plate 50 foreach section is illustrated as having 16 openings, while the plate 52has 72 openings. The openings, except for the bottom row in the plate52, are arranged so that one of the openings 54 is opposed to thecenter'of a'square of which the openings 56 form the corners, so thathigh pressure air from the supply duct 30 entering the openings 54 ofthe plate 50 strikes the imperforate ortion of the plate 52, whereby itsvelocity ead is reduced substantially to zero and a uniform, relativelylow pressure within the chamber is built up.

In the preferred4 construction, the holes are approximately 3/gths of aninch in diameter for both plates, the spacing between holes for theplate 50 and one and one-half inchesI for the plate 52. The separationbetween plates is small and may be as little as one-fourth of an inch.

The supply wall of the drying room, therefore, comprises in effect apressure chamber of small dimensions in the direction of the vof each ofthe walls 40 constructed as above described, the

4flow of air and having provision for entrance vv'ofjair into it atarelatively high Velocity while permitting exit of air into the dryingroom at a relatively low velocity as determined by the greater number ofholes in the plate 52. The air issuing from the holes 56 of the plate onthe drying room side of the wall 40 comprises a large number of closelyand uniformly s aced streams of air which are at a practica ly uniformVelocity because of the uniform pressure pressure chamber. The streamsare sufficiently close together so that there is a substantially uniformflow of air into the drying chamber. v

The return wall of each drying room, as indicated at 42, comprises aplurality of plates of the typel shown in Fig. 5, each of these-platesbeing similar' both 'as -to size, number, and arrangement of holesas theplates 50 of the supply wall. Since there is a relatively small numberof holes in the return plate, the`velocity head of the air as itapproaches the plate is largely converted into a pressure head whichgives a substantially uniform pressure over all parts of the returnwall. Under the influence of this pressure, the air is forced throughthe holes of the return wall at a relatively high velocity to enter thereturn ducts 32 and' 34 from which it passes into the air conditioning Aapparatus.

The construction of the supply and the return walls of the dryingchamber as above described, meets the most exacting requirements foruniformity of flow across the chamber and through the material to bedried. It is particularly advantageous in the drying of hard woods whereuniformit of flow is necessary. For the drying of so t woods wherein thefibers are not so closely compacted as to built up within the resist theevaporation of moisture to as high A a degree as in hard woods, thesupply wall of the pressure chamber may be built up of single platesconsisting either of the plates 50 alone or the plates 52 alone. For thesingle plate wall, the use ofl `plates 504 having the smaller number ofholes is preferable, not only because of the greater and therefore moreuniform building up of pressure on the supply side of the plate. v

From Fig. 1 it will be seen that the sides ducts 30 consists of two ofthe walls forming the sidesof adjacent drying ro ins. The ends of eachduct 30 are closed by a vertical imperforate plate 55.

The provision of the return wall opposite the supply wall of each dryingroom is a feature of great importance. If no wall were provided at thereturn side, the head of air on the return side of the material to bedried would not necessarily be uniform over the entiretransverse area ofthe drying room.

because of the smaller expense, but also v Instead of iiowing in pathsdirectl across the drying room, the air Would ten to dow" fromone sideof the drying room to the other will be substantially the same for allperpendicular distances between opposite walls.

The diiferences in head being uniform, the

velocities of air flow will therefore beuniform, and stream linesperpendicular to the Walls are thereby assured. All possibility ofuneven drying of the material is therefore avoided. Y

In the operation of my improved drying kiln the cars or trucks areloaded or stacked outside of the kiln With the lumber to be driedarranged in horizontal layers with transverse separators or stickersbetween the layers of lumber in the usual manner. The trucks are thenWheeled into the kiln, the doors closed, and the fan and conditioningapparatus set in operation.

' If hard Wood is to be dried, the double i partition supply Wall isused, and a pressure of from one-half to an inch of Water is maintainedby the centrifugal fan'in the air supply ducts 30. With the partitionsspaced as above described, and with the number, size and arrangement oforifices specified, the drying air Will pass through the opening 54 inthe duct partition at a relatively high velocity, approximately 3000feet per minute, creating a pressure in the pressure chamber in theneighborhood of one-quarter of an inch. From the pressure chamber theair Will pass through the orifices 56 in the inner partition and intothe drying chamber at a velocity of about 800 feet per minute, and willcreate an even and uniform fioW of air across the entire drying chamberof approximately twentyve feet per minute. From the drying chamber theair passes through the orifices in` the return Wall into the returnducts 32, through which it is led`back to the conditioning apparatus andthe centrifugal fan for recirculation.

If the wood'to be dried is of the softer varieties, the partition 50 inthe duct side of the supply Wall will be removed, permitting the dryingair to pass directly from the supply ducts through the orifice 56 on thepartitions orplates 52 into the drying room. A greater quantity ofdrying air at higher velocities Will, under these conditions, passacross the drying chamber, but owing to the construction of the supplyandreturn Walls,

'the new Win be unirqrmiy the am@ for n1 transverse sections of theroom.-

t will be understood that although the perforated Walls or partitionsare described `as forming the sides of the drying chamber, the inventionis not limited to a construction in Which these Walls are verticallydisposed, it being only necessary that they sha-ll be par- -vallel toeach other and arranged so that including a pressure fan and supply andre.

turn ducts connecting the fan and the drying room, and a pressurechamber through Which the air passes from the supply duct to the dryingroom comprising closely spaced, uniformly perforated partitions toafford a sub# stantially uniform pressure over all parts of the pressurechamber, the total area of the perforations in the supply side of thechamber being less than in the drying room side. i

2. A kiln comprising a drying room, a pressure fan and supply and returnducts for circulating air through the drying room, and a pressurechamber through `which the air passes from the supply duct to the dryingroom -comprising opposed closely spaced partitions each havingperforations .over their surfaces of approximately the samevsize butgreater in number in the drying room side of the chamber than in thesupply side to afford a substantially uniform pressure in all parts ofthe pressure chamber and a substantially uniform velocity of air intothe drying room.

-3. A kiln comprising a drying room, a pressure fan and supply andreturn ducts for circulating air througl.` the drying room, a Wall onthe supply side of the drying room comprising oppositely disposed,closely spaced partitions to form a pressure chamber, the oppositepartitions having uniformly arranged non-registering perforationswhereby-a substantially uniform pressure is permitted to build up in thepressure chamber to cause the air to flow with uniform velocity throughthe drying room.

4. A kiln comprising a drying room, a pressure fan and supply and returnducts for circulating air thro-ugh the drying room, and a pressurechamber forming a Wall'at the supply side of the drying room andincluding closely spaced partitions through Which the air passes to the'drying room, the partitions having non-registering perforations small innumber in the supply side to iis cause air to enter at a relatively highveing room being similar to the inlet plate of locity and maintain a`uniform pressure in 'the pressure chamber;

the pressure chamber, and relatively large in 9. A kiln comprising adrying room, means number in the drying room side whereby the forcirculating air through the drying room 5 air issues from the pressurechamber with including a pressure fan and supply and re- 70 a moderateveloclty into the drying room. turn 'ducts connecting the fanand thedry- 5. A kiln comprising a drying room, a ing room,- and a pressurechamber throughpressure fan and supply and return ducts which the airpasses from the supply duct for circulating air through the drying room,to the dr ing room comprising uniformly walls interposed in the path ofthe air flow perforate partitions spaced from one 1an-75 on oppositesides of the drying room to reother less than the minimum separationbesist the flow of air and tofmaintain the prestween perforations'in thepartitions to mainsure adjacent each wall, the wall on the suptain asubstantially uniform pressure over ply side ofthe drying roomcomprising opall parts of the pressure chamber and conpositely disposedspaced perforated plates structed and arranged to cause the air to soforming a pressure chamber through which flow with a substantially lowervelocity from the air from the supply duct passes, and the the pressurechamber to the drying room opposite wall having uniformly spaced perthanfrom the supplv duct to th'e'pressure forations to permit uniform flowthrough chamber.

the drying room, In testimony whereof I have signed my g5 6. A kilncomprising a drying room, a presname t0 this specification. l

sure fan and supplyl and return ducts for HAROLD F. HAGEN.

circulating air through the drying room, walls interposed in the path ofthe air flow on opposite sides of the drying room to re- 90 sist theflow of air and to maintain pressure adjacent each wall, the wall onthesupply side of -he drying room comprising closely spaced, uniformlyperforated partitions having a greater area of perforations in the dryl95 ing room. side than in the supply side, and l the opposite wall ofthe drying room beingv uniformly perforated, whereby substantiallj1uniform flows through the drying room are obtained.

7. A kiln comprising a drying room, a-pressure fan' and supply andreturn ducts for circulating air through the drying room, uniformlyperforated walls interposedinthepath '10 of the air ow on opposite sidesof the drying l m room to resist the fiow of air and to build up thepressure adjacent each wall, the wall on the supply sid-e of the dryingroom comprising a pressure chamber including closely spaced partitionshaving non-registering 11( perforations greater in number on the dryingroom side of such pressure chamber than on the supply side, whereby asubstantially uniform pressure is built up in the pressure chamber anduniform flow throughthe drying room is secured.

8. A kiln comprising a drying room, a pressure fan and supply and returnducts for circulating air through the drying room, 12| walls interposedin thepath of the air flow on opposite sides of the drying roomto resistthe flow of air and to build up the pressure adjacent each wall, theinlet wall of the l0 drying room comprising a pressure chamber 1- havingan inlet partition with regularly arranged holes and an outlet partitionclosely spaced thereto with a relatively large num-y ber of holes out ofregister with the holes in 05 the inlet plate, and the outlet wall ofthe dry- 1 rambla. 1,833,391.

cenrlrlcmi'or eommcrlou. n

` I 'I Granted November 24, 19317,` to I Itis hereby certified-thaterror appears in the printed soecificaton 'the l abovenumbered patentrequiring correction as follows: Page 4, lined,l c'iaiin 4, after"Y theword "moderate" insert the word uniform; and that the said Letten-lPatent should be read with this correction therein that thesamemay-confonn Y' to the record ofthe case in the Patent Office. V-.Signed md sealed this 9th day of February, A. D. j 1932.

M. J.' Moore,

(Seil) AetingConlnissioner'of Patenti.

